Colored light signal



Dec. 24, 1946. w WELLS 2,413,127

COLORED LIGHT S IGNAL Filed May 18, 1945 the roundel, but a smallPatented Dec. 24, 1946 COLORED LIGHT SIGNAL Wesley B. Wells,Wilkinsburg, Pa., assignor to The Union Switch & Pa., a corporationSignal Company, Swissvale, of Pennsylvania Application May 18, 1945,Serial No. 594,399

7 Claims. I

My invention relates to light signals, and particularly to light signalsof the searchllght type which are capable of selectively projecting aplurality of beams of light of dilferent colors from a single lightsource.

One well-known form of signal of the type described is shown anddescribed in an application for Letters Patent of the United States,Serial No. 548,108, filed by me on August 4, 1944, and comprises a lightunit for concentrating the light rays from an associated source at afocal point, a lens unit having a focal point which coincides with thefocal point of the light unit for converting the light rays from thelight source into a beam of substantially parallel rays, and a pluralityof color filters which are selectively interposed into the light beamadjacent the common focal point of the light and lens units to impart tothe beam the desired color. Heretofore, the color filters have usuallycomprised a flat glass roundel about one inch in diameter, and with theroundels constructed in this manner, external light rays entering thesignal through the lens unit are caused to pass through the focal pointof the lens unit whereupon they strike the side of the roundel nearestthe lens unit. The greater portion of each of these rays will passthrough percentage of each ray is reflected by the surface of theroundel. Some of the reflected rays are reflected in such directionsthat they will not reenter the signal beam, but other ones of these rayswill leave the signal through the lens unit in a beam which may beparallel to the signal axis. That is to say, ex-

ternal light entering the signal will be partially reflected by theroundels, and will leave the signal in the form of a beam which may beparallel to the axis of the signal beam and which covers the centralportion of the lens over an area. equal to approximately half of thelens area. Under the conditions most frequently encountered in practice,the intensity of the reflected light is insufllcient to produce anymaterial effect upon the signal indication. However, under certainadverse conditions such as in the early morning or in the late afternoonwhen the sun is near the horizon and the signal is so located that thesun can shine directly into the lens unit, the intensity of thereflected beam may become sufficiently great to fade out the signalindication, destroying its true color and materially shortening therange of the signal. The indication produced by such reflected light isgenerally referred to as a phantom indication, and the principal objectof my invention is to provide a novel construction of ro-undel whichwill prevent phantom indications in signals of the type described.

According to my invention, I construct the roundel with such a shapethat any external light rays entering the signal through the lens unitwill, if reflected only once by the rounds], be reflected in suchdirections that they will not reenter the lens unit, and, if reflectedmore than once by the roundel, will be so weakened that if they doreenter the signal beam through the lens unit, they will havesubstantially no efl'ect on the color or range of the normal signalindication. In the preferred form of my invention, the roundels are madeconical in shape, but it should be understood at the outset that I donot wish to limit myself to this particular shape.

Other objects and characteristic features of my invention will becomeapparent as the description proceeds.

I shall describe one form of light signal embodying my invention, andshall then point out the novel features thereof in claims.

The accompanying drawing is a. view partly in side elevation, and partlyin vertical section, showing one form of light signal embodying myinvention.

Referring to the drawing, the light signal in the form here shown is ofa well-known type in widespread commercial use, and comprises alightunit A, an operating mechanism B and .a lens unit C. The light unit Aand operating mechanism B are disposed within a suitable housing I,while the lens unit C is secured in place in front of an opening 2provided in the forward wall la of the housing I.

The lens unit 0 is of well-known construction and comprises a doubletmade up of two spaced lenses 4 and 5 mounted in the outer and innerends, respectively, of a tubular casing 6 commonly referred to as a lensbarrel. The two lenses 4 and 5 are of plano-convex type, and are bothclear or colorless. "Secured to the outer end of the lens barreldirectly above the outer lens 5 is a hood I which performs the usualfunction of shielding the lens 5 from the direct rays of the sun.

The light unit A comprises an electric lamp 10 having a concentratedfilament II, and an elliptical reflector I? which concentrates the raysof light from the filament H at a focal point 13 which coincides exactlywith the focal point of the lens unit C.

The operating mechanism B is similar to that disclosed and claimed inLetters Patent of the United States No. 2,172,724, granted to myself andanother on September 12, 1939, for Light signals, and comprises a topplate l5 having secured thereto a polarized electroresponsive motormeans (not shown) for operating between an intermediate and two extremepositions a spectacle arm I 5 which projects upwardly through an openingin the top plate into an auxiliary housing I! which is secured to theupper side of the top plate. The spectacle arm is provided at its upperend with three angularly spaced color filters which align respectivelywith two glass windows I8 and i9 according as the spectacle arm occupiesits one extreme position, its other extreme position or an intermediateposition midway between its two extreme positions. Only the color filterwhich is normally colored red is shown in the drawing, but spectaclearms of the type described are well known and it is therefore deemed tobe unnecessary to show this spectacle arm in detail herein.

The operating mechanism also comprises suitable contact mechanism notshown, operated by the motor means for controlling similar signals,relays or other apparatus forming part of a complete signal system.

The operating mechanism is removably secured within the casing I, and isso positioned with respect to the casing that the light rays emitted bythe light unit A will pass through the windows l8 and IS on oppositesides of the common focal point of the light and lens units, in themanner indicated by the dot and dash lines 2i. It will be apparent,therefore, that the signal will display an indication the color of whichwill depend upon the color of the particular filter which is inalignment with the windows.

As shown, the window [8 is flat, while the window I9 is convex.

As was pointed out hereinbefore, the purpose of my present invention isto prevent light rays which may enter the signal from outside the signalthrough the lens unit C from being reflected by the roundel back intothe signal beam in a manner which will cause a phantom indication, andaccording to my present invention I accomplish this result by so shapingthe roundels that external light, if directly reflected by the surfaceof the roundel nearest the lens unit, will be reflected in suchdirections that it will not reenter the lens unit, and if reflected morethan once by the surface of the roundel, will be so weakened inintensity that it will have no appreciable effect on the light beam.

In the preferred shape shown, the roundel 2B is conical and is disposedwith its apex facing the light unit in such a position that its apexcoincides with the axis of the signal beam. The roundel must have asufficient diameter and must be located sufficiently close to the commonfocal point of the light and lens units to completely intercept the beamfrom the light unit. Furthermore, in order to prevent external lightrays from being directly reflected into the lens unit, the ele ments ofthe cone must have such a slope that no light rays entering the signalthrough the lens unit will strike any element of the cone at rightangles.

With the roundels constructed as just described, their effect onexternal light rays entering the signal through the lens unit can bestbe illustrated by tracing th paths of a number of typical rays. Thepaths of these rays prior to striking the roundels are indicated by fulllines, while the paths of these rays after reaching the roundel areindicated by long dash lines or short dash lines according as the lightpasses through the roundel or is reflected by it. As shown, the paths ofeight typical rays, designated 22 to 28, inclusive, which enter thesignal through the top half of the lens unit and parallel to the signalaxis are illustrated, It will be noted that these rays upon striking thesignal lens 5 are concentrated by the lenses of the lens unit at thecommon focal point of the light and lens units, and after passingthrough this focal point, these rays diverge and strike the surface ofthe roundel nearest the focal point. The greater portions of these rayspass through the roundel, but a small percentage of each ray isreflected by the surface of the roundel. Any light which passes throughthe roundel will have the same color as the light entering the signalbeam from the light source and will not therefore have any tendency toproduce a phantom indication. It will be noted that those portions ofthe rays which are reflected directly by the roundel such as thoseindicated by the long dash lines 22, 23 and 24 are reflected in suchdirections that they do not reenter the lens unit. A portion of the ray29 which strikes the apex of the cone may theoretically reflect backupon itself so that it will leave the signal by the same path which itentered the signal, but the amount of this reflected light is too smallto cause any appreciable phantom indication. The rays 21 and 28 shownstriking the nearest side of the roundel will be partially reflected tothe opposite side of the cone where the majority of the reflected lightwill pass through the cone and a small portion will be reflected outthrough the lenses as shown by the long dash lines 21 and 28. Afterleaving the signal, these rays which are very weak due to being doublyreflected, are disposed at an angle to the signal axis and consequentlyhave very little or no eiTect on the normal beam from the signal.

It should be particularly pointed out that while as shown in the drawingthe conical roundel is disposed with its apex facing the light sourceand with its base facing the lens unit. the only reason for disposingthe roundel in this manner is because of space considerations in theparticular signal illustrated. With other well-known forms of similarsignals where clearances will permit, the roundel may be reversed inposition so that the apex faces the lens unit and the base faces thelight unit with equally good results.

One advantage of a, light signal embodying my invention is that itcompletely eliminates phan tom indication under the most adverseconditions encountered in practice.

Although I have herein shown and described only one form of light signalembodying my invention, it i understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a light signal comprising a light unit for concentrating the raysof light from a light source at a focal point which coincides with thefocal point of a lens unit which converts the light rays into a signalbeam of substantially parallel rays and means for interposing in thesignal beam adjacent the focal point a colored roundel to impart adistinctive color to the signal beam, the improvement which consists inproviding said roundel with substantially a conical shape to prevent itfrom directly reflecting back into the lens unit light rays whichinitially enter the signal through the lens unit.

2. In a light signal comprising a light unit for concentrating the raysof light from a. light source at a focal point which coincides with thefocal point of a lens unit which converts the light rays into a signalbeam of substantially parallel rays and means for interposing in thesignal beam adjacent the focal point a colored roundel to impart adistinctive color to the signal beam, the improvement which consists inproviding said roundel with substantially a conical shape to cause it todivert from the signal beam substantially all light rays striking itfrom a source outside of the signal.

3. A light signal comprising a light unit for concentrating the rays oflight from a light source at a focal point, a lens unit having a focalpoint which coincides with the focal point of the light unit forconverting the light rays from the light source into a beam ofsubstantially parallel rays, and a color filter interposed in said beamadjacent said focal point to impart to the beam 9. distinctive color,said filter being in the form of a cone the elements of which areinclined to the axis of the signal beam at such an angle thatsubstantially all rays entering the signal through the lens unit andstriking the surface of the cone will be reflected in directions whichwill prevent them from reentering the lens unit.

4. A light signal comprising a light unit for concentrating the rays oflight from a light source at a focal point, a lens unit having a focalpoint which coincides with the focal point of the light unit forconverting the light rays from the light source into a beam ofsubstantially parallel rays, and a, color filter interposed in said beamadjacent said focal point to impart to the beam a distinctive color,said filter being in the form of a cone the elements of which areinclined to the axis of the signal beam at such an angle that any raysentering the signal through the lens unit and directly reflected by thecone will be reflected in directions which will prevent them from re- 5entering the lens unit.

5. A light signal comprising a light unit for concentrating the rays oflight from a light source at a focal point, a lens unit having a focalpoint which coincides with the focal point of the 10 light unit forconverting the light rays from the light source into a beam ofsubstantially parallel rays, and a color filter in the form of a conedisposed in said beam adjacent said focal point with its axis coincidingwith the beam axis.

6. A light signal comprising a light unit for concentrating the rays oflight from a light source at a focal point, a, len unit having a focalpoint which coincides with the focal point of the light unit forconverting the light rays from the z light source into a beam ofsubstantially parallel rays, and a color filter in the form of a conedisposed in said beam adjacent said focal point with its axis coincidingwith the beam axis and with its apex closest to the light source.

7. A light signal comprising a light unit for concentrating the rays oflight from a light source at a focal point, a lens unit having a focalpoint which coincides with the focal point of the light unit forconverting the light rays from the light source into a beam ofsubstantially parallel rays, and a color filter interposed in said beamadjacent said focal point to impart to the beam a distinctive color,said filter being in the form of a cone the elements of which areinclined to the axis of the signal beam at such an angle that noexternal light rays entering the signal through the lens unit willstrike any element of the cone at right angles.

WESLEY B. WELLS.

